Vacuum dryer shelf temperature control



Aug. 19, 1969 L. c, COSTELLO ET AL 3,461,953

VACUUM DRYER SHELF TEMPERATURE CONTROL Filed Aug. 15, 1967 2 Sheets-Sheet l E3 Leonard C.Cos+e1lo Karl H.W1'egmann INVENTORS BY @QQQ 40- ggenf Aug. 19, 1969 Filed Aug. 15.

1.. c. COSTELLO ET AL VACUUM DRYER SHELF TEMPERATURE CONTROL 2 Sheets-Sheet 2 J E 44 EU 2 8 T J: \k 48 X 58 F5; (p2 54/ 60 If r F Leonard C.CO$I".UO Karl H.Wiegm c1nn INVENTORS @eQ-MQ fljenf' United States Patent ABSTRACT OF THE DISCLOSURE A plurality of vertically spaced hollow shelves in a vacuum dryer housing communicating with a pair of vertical manifolds which areTconnected selectively through a solenoid valve arrangement to a circulating source of heating fluidl A timerffcontrolled' switch'in the electric circuit of the solenoid valve etfelcts periodic reversal of flow of heating fluid through'the shelves.

Background of the invention This invention relates to vacuum drying apparatus, and more particularly to simplified meansforcontrolling the temperature of shelves within such apparatus.

In the vacuum drying of materials it is conventional practice to circulate a heated liquid through hollow shelves on which the material -to be dried is Supported. The heated liquid enters each shelf at one side and travels therethrough' to the opposite side, giving up heat to the material as it progresses through the shelf. As a consequence, greater amounts of heat are transferred to the material adjacent the entrance side of the shelf as compared with the exit side of the shelf. The drying rate thus tends to be faster forthe material adjacent the entrance side of the shelf.

Because of this temperature variation across the shelf and the possibility of damaging the material because of the temperature variation, it is common practice to maintain the heating liquid at a temperature lower than the material is capable of withstanding. This lengthening of the drying cycle represents decreased productivity of the apparatus and correspondingly increased cost of producing the final product.

Summary of the invention In its basic concept the present invention involves means by which a heating liquid is circulated through the shelves of vacuum drying apparatus periodically in opposite directions, whereby to maintain a substantially constant and uniform temperature over the entire area of the shelf.

It is by virtue of the foregoing that the principal objective of the foregoing invention is achieved, namely to overcome the disadvantage inherent in prior apparatus as discussed hereinbefore.

Another important object of this invention is the provision of vacuum dryer shelf temperature control means which is of simplified construction and which may be installed on existing vacuum drying apparatus with speed and facility.

The foregoing and other objects and advantages of this invention will appear from the following detailed description, taken in connection with the accompanying drawings of the preferred embodiments.

be associated shelf temperature control means of' the present invention.

4 Claims 7 Patented Aug. 19, 1969 ice FIG. 2 is a foreshortened sectional view taken on the line 2-2 in FIG. 1 and showing by dash lines the internalconstruction of a hollow vacuum dryer shelf.

FIG. 3 is a sectional vvie-w taken on the line 3-3 in FIG. 2.

''FIG. 4 is a schematic view in elevation of a vacuum dryer shelf assembly having incorporated therewith shelf temperature control means embodying the features of the present invention.

FIG. -5 is a schematic view in elevation, similar to FIG. 4, showing a second form of shelf temperature control embodying the features of the present invention.

Description of the preferred embodiments Referring particularly to FIG. 1 of the drawings, the apparatus illustrated includes a housing having a top wall 12,

a bottom wall 14, side wall 16, a rear wall 18 and a front door 20 removably closing the front opening of the housing. The door is secured in closed position by such means as the peripheral pressure screws 22, and a peripheral gasket 24 is interposed between the housing and door to provide a vacuum tight seal. A conduit 26 communicating through the rear wall of the housing may be connected to a vacuum pumping system for the purpose of evacuating the housing.

The housing contains within it a plurality of vertically spaced horizontal shelves 28. In the embodiment illustrated the shelves are of generally rectangular configuration and are supported in horizontal, vertically spaced apart relation by angle clips 30 or other suitable supports welded or otherwise secured to the inside walls of the housing.

As best shown in FIGS. 2 and 3, each of the shelves is of hollow construction. The chamber 32 within the shelf preferably is interrupted at spaced intervals by baffles 34 which extend alternately from opposite sides walls of the shelf and terminate inward of the opposite side wall. These baffles thus provide a tortuous path for the circulation of heated liquid from one side of the shelf to the other. Openings 36 and 38 in the opposite side walls of the shelf communicate the inner chamber 32 with a pair of fluid conduits 40 and 42 which are connected one to each of a pair of spaced, vertically extending manifolds 44 and 46, respectively.

I accordance with the present invention the manifolds are connected to a source (not shown) of heated fluid in such manner as to effect circulation of the heated fluid periodically in reverse directions through the shelves. In the embodiment illustrated schematically in FIG. 4 the manifolds 44 and 46 are connected through the conduits 48 and 50, respectively, to pair of ports of a suitable conventional solenoid valve 52. The inlet port of the valve is connected through the inlet conduit 54 to the pressure outlet of a circulating pump, and the return port of the valve is connected through the return conduit 56 to the container in which the fluid is heated, as will be understood.

The coil 58 of the solenoid is connected through a control switch 60 to the terminals 62 of a source of electric potential. The control switch is actuated by a timer device 64 which, in the embodiment illustrated, is an electrical timer connected to the terminals 62 of the electric supply.

In the operation of the control system illustrated in FIG. 4, let it be assumed that when the control switch 60 is open and the solenoid is deenergized, the valve 52 is positioned to communicate the pressure feed conduit 54 with the conduit 48, and the return conduit 56 with the conduit 50. Thus, heated fluid is circulated through the shelves 28 from left to right. After a predetermined interval of time, the timer 64 effects closure of the control switch 60 and energizationof the solenoid coil, to.v

move the valve to communicate the pressure feed conduit 54 with the conduit 50tand the return conduit 56 with the conduit 48. Heated fluid thus is circulated through the shelves from right to left. This reversal of flow of heated fluid through the shelves thus serves .to maintain the shelves at a substantially constant and uniform temperature throughout their areas.

In the modification illustrated in FIG. 5 the pair of manifolds 44, 46 communicate at their top and bottom ends through the solenoid valve 70 and 72 with feed and return conduits 74 and 76, respectively, associated with a source (not shown) of heat fluid. In the illustrated positions of the valves, heated fluid is caused to pass through the shelves from right to left. By rotating both valves 90 clockwise the heated fluid is caused to pass through the shelves from left to right. The coils of the solenoids may be connected together electrically in parallel and connected to a source of potential through a timer controlled switch in manner similar to that illustrated in FIG. 4.

It is to be noted that the shelf temperature control system of the present invention is mounted outside the vacuum drying apparaus, and thus may be added to existing apparatus with speed and facility. Further, the sys tem of the present invention may be utilized not only to control the flow of beating fluid through the shelves but also of a refrigerant which may be circulated through the shelves prior to the circulation of heating fluid in freeze drying applications, as will be understood.

Further, the shelf temperature control system of the present invention may be incorporated in vacuum drying apparatus which also accommodates the stoppering of containers in which the material has been dried. In such apparatus the hollow shelves are mounted for movement toward and away from each other so that the partially slotted or grooved stoppers which initially are seated only partially in the containers are brought into abutment with the underside of the next upper shelf and pressed securely into the containers.

It will be apparent to those skilled in the art that various changes may be made in the size, shape, type and arrangement of parts described hereinbefore. For example, the fluid control valves may be operated manually, or by mechanical, pneumatic or hydraulic type actuators, rather than by the electrical system described. Mechanical time-rs may be employed in place of the electrical timer illustrated.

Having now described our invention and the manner in which it may be used, we claim:

. 1. In vacuumdrying apparatus having a plurality .of vertically spaced hollow shelves communicating through a pair of vertical manifolds with a circulating source of heating fluid, wherein said source includes feed and return conduits, the combination therewith of control means for reversing the direction of flow of heating fluid through the manifolds and shelves, comprising adjustable fluid control valve means interconnecting the manifolds and said feed and retu rn conduits and operable in one position of adjustment to communicate one manifold with the feed conduit and the f.0'ihf manifold with the returnconduit, and operable in a second position of adjustment to communicate said other manifold with the feed conduit and said one manifold with the return conmeans interconnects the upper end of one manifold and the lower end of the other manifold selectively to the feed and return conduits.

4. The combination of claim 1 wherein the valve means interconnects the lower ends of the manifolds selective- 1y to the feed conduit and the upper ends of the manifolds selectively to the return conduit.

References Cited UNITED STATES PATENTS 1,067,411 7/1913 Dupuy 165-97 2,623,449 12/1952 Losee 16512XR 2,677,243 5/1954 Telkes 165 12 XR 2,919,114 12/1959 Ljungstrom 16597 XR FOREIGN PATENTS 608,431 9/1960 Italy.

372,690 10/1963 Switzerland.

FRED C. MATTERN, JR., Primary Examiner MANUEL ANTONAKAS, Assistant Examiner US. Cl. X.R. 34-92; l97 

